1. Field
The present disclosure relates to a push button switch device including a self-illumination push button member, and a sewing machine provided therewith.
2. Related Art
A household sewing machine includes a push button switch device, such as a start/stop switch, provided on the front of an arm constituting a sewing machine body, for example. The push button switch device of the aforementioned type comprises a push button member which is mounted on a cover constituting the front of the arm so as to be depressible. With this, a switching element such as a “tact switch” (a registered trademark) is mounted on a substrate provided inside the cover, so as to be actuated by the push button member.
A self-illumination push button switch device is also provided which can display an operated state thereof (on or off state) in such a manner that a user can easily recognize the state of the switch. The self-illumination push button switch device includes a push button member made of a translucent material and light sources provided at a rear surface side of the push button member. For example, when the switch is in an on state, the whole surface, an outer peripheral ring, a mark and characters both provided on the surface or background is illuminated by light from the rear side.
A first conventional self-illumination push button switch device includes a cylindrical cap-shaped push button member, a light-emitting diode which is mounted on a substrate at the rear side of the push button member so as to correspond to a central part of the push button member, and a switching element is provided at a decentered position on a periphery of the push button member.
A second conventional self-illumination push button switch device includes a circular push button member made of a light-transmissive resin, a switch element provided along the central axis on a rear surface of the push button member, and plural light sources (LEDs) provided at respective positions displaced from a central axis of the switching element.
A third conventional self-illumination push button switch device includes a push button member made of a light-transmissive resin, a switching element and light-emitting elements serving as light sources. A mask member is provided on a rear surface of the push button member to guide light from the light-emitting elements to a predetermined position on the push button member.
The above-described first to third conventional switch devices have the following disadvantages. Since the switching element is decentered with respect to the push button member in the first conventional switch, a central axis of the push button member does not correspond with an operation axis of the switch element. As a result, the first switch device has a low operability, for example, providing a bad operation feeling when the user depresses the push button member.
The second switch device provides a good operation feeling since a central axis of the push button member substantially corresponds with an operation axis of the switching element. However, this necessitates locating the light sources (LEDs) at the respective positions displaced from the central axis of the switching element. Accordingly, it is difficult to uniformly illuminate the whole surface of the push button member. As a result, for example, the central part of the push button member is darker than the peripheral part of the push button member. Thus, the second switch device lacks in uniformity of brightness, resulting in a defect of low visual effect.
The third switch device includes the push button member having a good operation feeling and the mask member which can guide the light from the light-emitting elements to a necessary position on the push button. As a result, variations in the brightness can be reduced. However, provision of the mask member increases the number of components and complicates the structure of the switch device.
Thus, each of the above-mentioned conventional push button switch devices has an advantage and a drawback. Consequently, a push button switch device has been desired which has a good operation feeling, can uniformly illuminate the whole surface of the push button member, and can achieve these features by a simpler structure.